Science

Fast Radio Bursts observed

The universe is a vast and mysterious space, filled with distant and puzzling objects, but UW-Madison physics professor Peter Timbie has played a huge role in helping to demystify it by giving us a deeper understanding of the incredibly rare cosmological phenomenon called Fast Radio Burst: a singular pulse of radio signal.

Timbie and his lab work with understanding the early universe, using large radio telescopes to detect the signals emitted by distant pulsars, which are neutron stars that emit regular and repeated radio wave signals across the universe.

During a radio survey using the Green Bank Radio Telescope in Green Bank, Va., they heard that a research group in Australia had detected over ten Fast Radio Bursts, or FRBs. Timbie decided to analyze the data his team had already collected using the Green Bank Telescope, looking for any signs of previously unnoticed FRBs.

Using a new algorithm developed by members of Timbie’s lab, they were able to find one FRB in over 650 hours of archival data. That single FRB, found using the help of the Green Bank Telescope, has provided the clearest image yet of what a Fast Radio Burst is.

“What’s special about these is that they are just pulses, a single pulse,” Timbie said. “In some direction in the sky that we happen to have the telescope pointed, we see for a very short time—one millisecond—we see a little blip in the brightness of the signal.

Then it goes away, and it doesn’t repeat, and even though we’ve gone back and looked in the same spot many times, they haven’t come back… It’s a lot like a pulsar that forgot to come back.”

This phenomenon is rarely seen, as most objects emit repeating signals. Because of their unusualness, no one actually knows for sure exactly what is giving off FRBs. Timbie hypothesizes that FRBs may be emitted very distant pulsars. Regular pulsar signals will occasionally have phases where they become very bright, so according that Timbie’s model, it is possible that FRBs were simply not seen before because the pulsars emitting them were in their dim state.

FRBs, Timbie suggests, are simply from pulsars in their brighter and more visible stage.

To add to the mystery of FRBs, there is strong evidence that they are not from our galaxy. When observing the sky, scientists will divide it into the galactic plane and out of the plane.

The galactic plane consists of what we see in the Milky Way, our own galaxy; this plane contains most of the stars, nebulae, planets and other objects that we can see.

Outside of that plane, meaning essentially outside of our galaxy, the things that can be observed lessen greatly. Using the data Timbie’s group had analyzed, they concluded that the FRBs came from outside the galactic plane, suggesting that they originate from other galaxies in the universe.

Timbie estimates that they could be as far out as six billion light years, about half the age of the universe.The gains from this detailed understanding of FRBs are very exciting and important to the field of astrophysics.

The new algorithm that Timbie’s team created to detect FRBs in data can now be used as a tool for future studies of FRBs; without the software they wrote, it could have taken take years to fully sift through the data.

Their research on FRBs has also helped provide insights to other research fields; the UW-Madison physics research group that uses the IceCube to detect particles called neutrinos have also started looking into the same chunk of space where the FRBs originated from, as it is a possibility that neutrinos come from the same source as FRBs.

In addition, Timbie said, “if we can use [Fast Radio Bursts] as extra tools for measuring distances in the universe, that would be a strong application for mapping the universe.”

Mapping the universe, and particularly the early universe, is of special interest to Timbie – he specializes in studying “the oldest light in the universe”: light that is so old that it originates roughly around the same time as the famous Big Bang itself.

In essence, it is a snapshot of the universe in its infancy – around 13.4-13.7 billion years ago.

By having tools like FRBs which impressively stretch across half that immense distance and thus provide a snapshot of the universe at six billion years old, measuring huge cosmological distances becomes much easier.

The discovery of Fast Radio Bursts has raised many questions, adding upon the plethora of mysteries the universe has to offer, but with the new understanding that Timbie and his team have found, Fast Radio Bursts have proven to be fascinating and important pieces of the mosaic of the universe.